Many modern newspaper factories employ pyrofax photostatic film during the printing process. The film, often referred to hereinafter as a web, is in the form of an elongated thin member having a plastic image side and an opposed metallic back side. The web is about one and one-half feet wide and several hundred feet long so that it can be conveniently wound up on a central core into the form of a cylinder to facilitate the handling and storage thereof. One cylindrical roll of the web material contains sufficient material to enable the average size newspaper plant to print newspapers for several days. The film is marketed by the 3M Company of Minnesota and is sometimes referred to as Pyrofax Photostatic Film.
In printing newspapers, a master copy representative of a newspaper page is transferred onto the image side of the web, and thereafter the image is transferred from the web onto a transmat, and thereafter onto aluminum printing plates by a thermo process, thereby enabling the newspaper printing press to print the newspaper. Accordingly, the width of the web is approximately the width of a page of the printed newspaper.
After the image or indicia contained on the image side of the web has been transferred onto the transmat, the web is stored in a rolled up cylindrical configuration, usually upon one of the old used cores. Conventionally, the image side of the web is located to form the inner surface of the cylindrical roll of used web material.
It is known to remove the indicia from the image side of the web, as evidenced by Miles, et al U.S. Pat. No. 4,326,315. In the Miles, et al patent, a plurality of spaced parallel bunny brushes rotate about the central axis thereof, and are brought to bear against the image side of the traveling web. A considerable leading and trailing end of the web is sacrificed each time the web is reprocessed, with the loss of the leading and trailing marginal ends of the web being proportional to the length of the processing equipment, which is considerable and may amount to as much as 10-15 feet. Moreover, in the Miles et al process, the web can be reprocessed or rejuvenated only a limited number of times because the delicate image side of the web is harmed each time the web passes through the guide rollers and bunny brush assembly of the Miles, et al process equipment.
In the past, it has been proposed to clean dust and foreign objects from a film strip by utilizing vacuum, an elongated wiping cloth, and means for removing static electrical charges from the surface of the strip, as exemplified by Lindsay, U.S. Pat. No. 3,641,605. In the Lindsay patent, it is not contemplated to remove the indicia from a web, but rather it is contemplated to remove the unwanted foreign material from newly manufactured film so that the film is made available in clean, sterile condition.
Others have proposed engaging an elongated web, or a cylindrical drum, in order to remove indicia from the surface thereof as evidenced by the following patents:
______________________________________ Klett 4,230,406 Eichorn, deceased 3,893,416 Severynse 3,534,427 Martino 4,148,576 Sadamitsu 3,795,025 Taylor 3,706,108 ______________________________________
However, none of these references suggest that an elongate web of pyrofax photostatic film be rejuvenated according to the method and apparatus of the present invention.
The present invention differs from the above prior art both mechanically and conceptionally. In the present invention the image side of the web is forced to travel circumferentially a limited distance about the outer peripheral surface of a rotating cylindrical wiping cloth. The cylindrical wiping cloth engages the web while at the same time it revolves at a speed to provide a gentle wiping action and thereby completely clean the entire image surface of the web, whereupon the rejuvenated web can then be reused many more times in the newspaper printing plant by repeating the rejuvenating process set forth herein.